Hydrated lime has the chemical formula Ca(OH)2. It is also referred to as calcium hydrate, caustic lime and slaked lime. It is typically prepared by the action of water on calcium oxide. It is known to be a skin irritant and has a TLV of 5 mg/m3 of air.
It is advantageous for hydrated lime to be mixed into an aqueous slurry for easier and safer handling as well as facilitating easier processing. For example, hydrated lime is often sold in aqueous slurry form to minimise health and safety problems or to assist in applying the material through metered dosing units. These aqueous slurries may be used in the preparation of plasters and cements. Other uses include water treatment, road stabilisation, steel making and metals extraction. In water treatment applications, it can be used to neutralise acid wastes from many industrial processes and to help flocculate particles that are suspended in water.
Slurries with high concentrations of solids are generally more attractive in the marketplace because transport and handling costs per tonne of dry matter are lower. However, these high solid slurries are more viscous and more difficult to handle. Accordingly, there is a “trade-off” between the desirable high solids and low viscosity.
Dispersants or viscosity modifiers are known, which can be added to an aqueous slurry or paste to lower the viscosity and improve the flow characteristics of the slurry which in turn makes the high-solids product easier to handle. However, many of these additives are toxic and are therefore not suitable for applications involving food or potable water.
It would be desirable to have non-toxic dispersants for the hydrated lime slurries so that the slurries can be safely used in food or water treatment applications.